Restoring & Mixing Chicago At The Isle Of Wight

Tim Jessup in Chicago’s mix room, Sedona, Arizona.

A combination of modern technology and skilled engineering has allowed Chicago’s landmark festival performance to be released, almost 50 years after it was taped.

Chicago’s performance at the 1970 Isle Of Wight Festival has become the stuff of rock legend. Three years earlier, the band had been playing dank and conservative midwestern clubs; on 28th August 1970, they had flown across the Atlantic specially to play for an audience of hundreds of thousands at Afton Down on the Isle Of Wight. The set showcased the band at their most ambitious, unafraid of fusing genres and expressing their unbridled energy on a grand scale.

This memorable set was captured for posterity, but quality issues meant that the recording remained in the vaults for almost 50 years. In April, however, Chicago at Isle Of Wight was finally released by Rhino Records as the first two discs of the boxed set VI Decades Live (This Is What We Do), following painstaking restoration and a new original mix by the band’s own mix engineer Tim Jessup. Working out of the band’s hybrid studio in beautiful Sedona, Arizona, Jessup brings over four decades of experience in recording, mixing and sound design for music, film and television to his work with the band.

Local Hero

Tim’s work with Chicago began in 2010 after he met Lee Loughnane, a new Sedona resident and original member of Chicago. At the time, the band were finishing a concert DVD/Blu‑Ray titled Chicago In Chicago, featuring the Doobie Brothers. Management wanted Lee to fly to LA to oversee the 5.1 mix for the concert film, but Lee was home between tours and asked management to find someone in Sedona who could provide 5.1 mixing services so he would not have to be away from his family. As Tim tells the tale, the mix was a “Herculean effort” as he only had five days to complete the entire 26‑song set before delivery for manufacturing. Tim mixed for five days straight! In the end, “No‑one died, and everyone was relieved and happy with the results. It reminded me of my early days as a staff engineer at Kendun Recorders in Burbank, when I would typically not leave the studio for three days at a time. Learning to push yourself like that develops an obsessive work ethic that you never forsake. Now, at 60 years old, I still work the occasional all‑nighter.”

Chicago In Chicago would not be the last engineering miracle Tim would perform for the band. He designed the mobile recording studio known as The Rig used for their 2014 album Now XXXVI, and was the sound mixer for the film Now More Than Ever: The History Of Chicago, directed by Peter Pardini and released in 2016. The film was mixed in the studio that he designed and built for the band in Sedona, and which is a sonic replica of the many Tom Hidley rooms that Tim worked in early in his career.

Fast forward to the Autumn of 2017, when Lee approached Tim with a new project: mixing Chicago’s archival multitrack from the 1970 Isle Of Wight show, a festival that is sometimes called Britain’s Woodstock. Tim instantly knew the gravity of this task. A previous mix of the set, undertaken in the late 1990s, was once considered for release and rejected, owing to the poor sound quality of the original eight‑track source tapes. Tim’s “initial impression was that the Isle Of Wight project would likely never be mixed again, and that I would have only one chance to get it right for all time! But, no pressure.”

I asked Tim what had changed over the past two decades. “In a word, everything. Very powerful and effective restoration tools have evolved recently, such as iZotope’s RX software, that can accomplish what was simply impossible 20 years ago.”

Even so, Tim knew that, “Even with such powerful restoration tools and mega computer automation, Isle Of Wight would present serious challenges and require unconventional techniques to draw out a mix that both the band and the fans would care to lavish in. From the outset, I believed it could be accomplished, but I also knew it would be rife with unknown challenges, demanding solutions that I had yet to envision.”

In all, Tim remixed the entire show five times, “using eight different pairs of monitors, wrestling to get the mix to translate properly on the widest array of home speakers, remixing once again after mastering engineer Dave Donnelly took his first mastering pass at it.”

Chicago Transfer Authority

The source tapes had been recorded by the Pye mobile truck, overseen at Isle Of Wight by the CBS team of engineer Stanley Tonkel and producer Teo Macero. Columbia Records had originally intended to release the recordings as a live album, but the idea was dropped in favour of the band’s performance at Carnegie Hall, released as Chicago IV in 1971.

A tantalising glimpse into the interior of the Pye Mobile at the 1970 Isle Of Wight Festival. The recording of Chicago’s set was supervised by engineer Stanley Tonkel (left) and producer Teo Macero (right); another engineer, Vic Maile — who would later go on to record Motorhead’s ‘The Ace Of Spades’ — catches up on some much‑needed sleep!Photo: the Estate of Stanley Tonkel

The source tapes, “four reels of one‑inch, eight‑track tape,” are now in the possession of Warner Music Group, the parent organisation of Rhino Records. Tim reports that the recordings were “physically, in great shape. Tapes that are newer than 1972 have a back coating that becomes brittle and sheds badly over time. These tapes must be baked to re‑adhere the back coating before they can be safely played. The Isle Of Wight tapes from 1970 had no back coating and played beautifully. Amazingly, magnetic print‑through was also not an issue.”

The original reels “had been copied at Back Pocket Recording Studios in New York, not long after the show. There was no way of knowing whether they had been transferred using the European CCIR equalisation curve, or the American NAB curve. We had to listen to the tapes with each calibration curve and choose which one translated best. The CCIR curve has more of a high‑frequency roll‑off, like a pseudo‑Dolby effect, so the tape hiss was quieter, and the tracks sounded warmer, punchier and fatter with the European curve, especially Danny’s drums and Terry’s guitar. Even if the NAB curve was correct, we preferred the sound of the CCIR curve and that is what we used.”

Tim Jessup credits the studio’s Burl Audio A‑D converters with preserving and enhancing the sound of the original source tape.The studio set up by Tim Jessup for Chicago is a hybrid affair, and his Pro Tools mixes are fed through these Chandler summing mixers.The first step in the process was a new digital transfer. Project coordinator Jeff Majid booked time at Penguin Studios in LA and Tim made the eight‑hour trip, driving Chicago’s Pro Tools HD rig, along with their Burl Audio B‑80 Mothership interface, from Sedona to Los Angeles. It paid off in sound quality as “the Mothership would enable the digital files to sound indistinguishable from the original analogue tapes. The interface is unique because it has a very robust over‑built analogue front end, much like the Studer A827 tape recorder used for the transfer, with transformers on every input. Compared to most any other digital interface, the sonic difference is night and day. We mix through the B‑80 interface in the studio, and sum to stereo through our Chandler replica of the EMI TG12345 console from Abbey Road, circa 1969, the same mix bus that brought us Pink Floyd’s Dark Side Of The Moon.”

Plugging The Gaps

The transfer process made apparent one of the greatest challenges of the mix: the source tape was missing entire sections of several songs, apparently because ”the Pye Studio engineers had only one multitrack tape recorder on their remote truck, with no backup machine running to catch entire songs when the tape ran out during performances. They were changing reels of tape when the band began to play ‘Beginnings’, and lost the entire intro and part of the first verse. Similarly, the tape ran out right in the middle of ‘Does Anybody Really Know What Time It Is?’, losing part of a middle verse, a full chorus and part of the following verse.”

To create full versions for both songs, Tim created matching ‘grafts’ for the missing parts from an entirely different performance. Fortunately, Jeff had brought the two‑inch, 16‑track reels of the band’s 1971 Kennedy Center show to the transfer session, so they grabbed the missing song sections from these tapes. The process of creating the grafts was, says Tim, “one of the most surgical operations of the entire mix. The two shows sounded entirely different and ‘Beginnings’ was played at almost half‑speed during the Kennedy Center show. I had to tempo‑match the two performances by using iZotope RX to time‑compress each of the 16‑tracks until I found the perfect match. The amount of compression needed was extreme and most time‑compression software creates really nasty artifacts when it’s pushed that hard. But RX was clean as a whistle, thankfully. Each track was also slightly pitch‑shifted to match Isle Of Wight, including the drum tracks, so the leakage would remain in tune.

“Then began the task of matching each instrument’s sound between the two shows, though they were recorded with entirely different microphones, preamps, a different tape format, different guitars, different keyboards, and entirely different environments — an outdoor rock festival vs indoor concert hall. I actually had to dumb down the Kennedy Center tracks and make them sound more low‑res than they actually are to get them to match sonically. The grafts turned out to be very seamless and saved both ‘Beginnings’ and ‘Does Anybody Really Know What Time It Is?’”

You Hum It, I’ll Remove It

Another challenge was removing the 50Hz hum embedded in the audio. While “this is usually easy to remove, the Isle Of Wight stage, running 240 Volts, had some severe ground loops that created particularly nasty buzzes, with up to 12 audible harmonic overtones. Each overtone had to be precisely identified and individually removed using a combination of iZotope’s RX software and Universal Audio’s Massenburg 48‑bit parametric equaliser. The latter is quite the fine surgical tool, and helped to speed up the process of identifying each of the offending buzz harmonics for removal. Obviously, the goal was to take out all of the buzz components without changing the tonality or character of the musical instruments, or introducing any strange artifacts into the recording.

“Earlier in the show, there were also problems with microphone feedback on stage, especially on ‘Mother’ during James Pankow’s trombone solo. RX handily removed the feedback entirely. I spent a full week just tracking down and deleting buzz harmonics, listening for the effects on the instruments and then, finally, removing tape hiss from all of the tracks without diminishing the upper harmonics of the instruments. Each track was rendered perfectly pristine throughout the entire show, even during the band’s banter on stage. I also discovered many clicks and pops that showed up as audio spikes across all eight tracks throughout the show. A Wacom graphic tablet and pen were used to manually draw out each spike.”

Precision Gating

Despite the recording’s age and the challenges of its environment, the clarity of each instrument in Tim’s mix is very apparent, thanks to more detailed and painstaking work at the preparation stage. His approach has its roots in the early 1980s, when, as a second engineer to Barney Perkins, Tim was charged with writing all of Barney’s channel mutes on Kendun’s B‑series SSL console, in the infamous Studio D. “I managed or deleted all of the microphone leakage on stage that was possible to remove or attenuate. For instance, all of the brass were recorded to only one of the eight tracks. When the horns are playing, the stage leakage is naturally masked by their close proximity to the mics. But during rests, or between notes, the leakage is very apparent and washes out the mix. I manually edited out all of the leakage between notes, much like a noise gate but with adjustable fades. When the brass are not playing, their track is silent. I did the same with the vocal mics, Robert’s keyboards, and so on. Whenever instruments are not playing, their channel is muted. Each track became a patchwork of play regions on the Pro Tools timeline. The adjustable region fades, along with the unbridled overhead drum mic leakage, masked the editing and made it all sound very seamless.

“Unfortunately, this process also removed most of the natural stage ambience, so I used a combination of sculpted digital reverbs and delays to recreate the natural sound of the stage ambience and better control its balance against the instruments. The unedited tracks were literally drowning in ambience and leakage and sounded like a bootleg.”

The Inovonics 201: a secret weapon for drum mixing.The drums, recorded to only three tracks of the tape, required “more attention than anything else in the mix”. The overhead mics were copied to eight tracks in Pro Tools and, in all, 10 tracks were dedicated to the drums, with “three stereo pairs of overhead mics involving various degrees of parallel compression, blended with the uncompressed main stereo pair. One pair of overhead tracks were intensely but ‘musically’ limited by an outboard pair of vintage Inovonics 201 limiter‑compressors. This device was a secret weapon of a handful of top engineers in LA during the ’70s and ’80s, such as Bruce Swedien, who recorded Michael Jackson.”

As Tim’s mentor at Kendun Recorders, mix engineer Barney Perkins “would not do a mix session without a pair of Inovonics 201s on hand, as they were an essential part of his unique fat sound. He once cancelled a session after starting to mix, because the studio’s only pair of 201s were in use in another room!

“In addition to the overhead processing, the kick drum track was also copied, and each kick beat was isolated as its own region. After compression and EQ, the edited kicks were blended into the original linear track like a sample, providing the more intimate sense of moving the mic inside of the drum.”

One Guitar, Three Amps

Chicago’s induction into the Rock & Roll Hall Of Fame in 2016 drew deserved attention to the legacy of guitarist, singer‑songwriter, and de facto band leader Terry Kath, who passed away in January 1978. Tim understood the importance of getting Kath’s guitar track to sound upfront and prominent. Terry played a Gibson Les Paul Professional for most of the Isle Of Wight set, through the festival’s backline Vox amp, “with a prominently mid‑range‑forward speaker cabinet”.

This setup “did not produce the beefy tone that Terry later became known for, nor did the Les Paul Professional have the bite of Terry’s later guitars, such as his infamous Pignose Telecaster”. To better define Terry’s guitar in the mix, Tim re‑amped the isolated guitar track “through three separate guitar amplifiers simultaneously, which are then blended back into his original Vox guitar track perfectly in phase. Amp number one is a vintage Music Man that came straight out of Chicago’s warehouse in LA, an amp that Terry likely played through at one time. Amp number two is a vintage 1964 Ampeg flip‑top B‑15 bass amp, which provides a thick, warm bottom end to his tone. Amp number three is Lee’s modern Egnater that normally lives in the studio. All three amplifiers were recorded with API mic preamps, for their distinctive, beefy tone.”

One original guitar track thus turned into four separate Pro Tools tracks. Each was processed individually before the four tracks were then grouped together to lock in their tonal balance, and the levels were then automated as one guitar track. As Tim explains, “I don’t like to bounce tracks together if I can avoid it. The four guitar tracks are routed to a stereo pair of analogue inputs on our Chandler summing mixers and panned to appear wider, filling out the left side of the mix, rather than emanating from a single point. The six guitar input transformers, on both the Mothership interface and the Chandler summing mixers, also add a weighty, beefy character to Terry’s overall guitar sound, giving it more of an intimate and fat studio character.”

To obtain the necessary depth and punch from Terry Kath’s guitar, Tim Jessup split it out to three additional tracks and reamped them through different amp and mic setups.

Tim’s inspiration was the work of engineering icon Al Schmitt, who, he says, “has long preferred to move or change a microphone on an instrument, rather than use EQ at all. Re‑amping Terry’s guitar was a similar organic process, much more effective and harmonically rich than reaching for an EQ on a console. It was like having Terry back in the studio for a few short hours, and it gave me a much bigger guitar sound to work with. In addition, three separate 48‑bit Massenburg EQ plug‑ins were used, each one corresponding to one of Terry’s three pickup switch positions on his guitar. Whenever he switches his pickups during the show, a different EQ is engaged which is optimised to that particular switch configuration.”

Tim’s approach to mixing the raw multitracks saw the three original drum tracks multiplied into numerous parallel tracks with different processing.

Doing The Splits

Vocally speaking, the classic Chicago line‑up was based around the combination of Terry Kath’s baritone, Peter Cetera’s tenor, and the voice of Robert Lamm, which lay between the two ranges. They had been recorded through relatively low‑quality stage mics, and the three vocal parts had been squeezed onto only two of the eight tracks on the tape. Tim “separated each vocalist and gave them two individual Pro Tools tracks each, with their own unique signal processing and EQ. The harmony background vocals were also moved to a separate track and ‘stereo‑ised’ to emanate from both sides of the mix, surrounding the lead vocals in the centre. This really helped to open up the vocals and give them much better definition and presence overall. Unwanted or harsh frequencies, inherent from the dynamic microphones, were removed using quite a bit of subtractive EQ, making funky inexpensive microphones sound a lot more expensive!”

Tim used a similar process on Robert Lamm’s keyboards, which were also combined onto a single track of the tape; at the mix, “all of his Hohner electric piano sounds and his Hammond B3 organ were each separated out onto their own individual tracks for tonal and dynamic optimisation. On ‘Colour My World’, the electronic‑sounding Hohner keyboard wasn’t quite up to the task for that iconic piano part. Considering what might be appropriate to enhance the sound from that era of technology, I used the Waves version of the Abbey Road ADT (Artificial Double Tracking) invented for the Beatles vocals. It’s subtle, but it makes the track more harmonically piano‑like, with multiple strings for each note, and a little less like a harpsichord.”

From only two original vocal tracks, both heavily affected by spill, Tim Jessup created this patchwork of separate regions and tracks.

The Parallel Path

In total, the original eight tracks of the Isle Of Wight recording became almost 50 tracks on the Pro Tools final mix, including the 10 drum tracks, four guitar tracks and eight vocal tracks. I asked Tim what the band thought of his work from their perspective of reacquainting themselves with their early years. “Robert Lamm had initially expressed his concern about whether the Isle Of Wight recording could be turned into a commercially viable master, given their failed attempt in the late ’90s.” After hearing Tim’s treatment of the recording, however, Robert called the result an “enhanced mix”. As Tim says, “No‑one expected we could extract this much clarity from the original tracks.”

The overall sense of clarity and definition was enhanced by an additional stem‑mixing stage. “Many top engineers use their own unique parallel compression methods on their final mixes to make them sound as big and as loud as possible. After considering what might work well as the icing on the cake, I developed an idea that seemed well suited to preserve the dynamics of the mix, while increasing overall presence. I made individual stems of each main part of the mix: Terry’s guitar, the vocals, the brass, Robert’s keys, Peter’s bass and Danny’s drums. Next, I imported the final stereo mix into a new Pro Tools session, along with each of the stems. Each stem was then individually compressed and blended very slightly into the final mix, with their respective levels automated throughout the show. Rather than using parallel compression across the entire stereo mix bus, I adjusted the compressed stems individually according to their dynamic relationship to the full mix at any given point in time.

The final stage in Tim’s mix process was to export stems that encapsulated his detailed instrumental edits and processing, and use parallel processing to ‘glue’ these together.

Very subtle use of the stems went a long, long way in bringing out more presence, without diminishing the dynamics of the mix. Perhaps only five to 10 percent of the stems at any point were used. Ultimately, this is why Terry’s guitar and the vocals sound so present and the drums are also so solid, though they were recorded with very few microphones. The Isle Of Wight mix represents a number of unconventional and innovative ways to resolve severe archival audio issues, while preserving the beloved character of its analogue sound. But mostly, it’s just plain fun to listen to, and that’s really what it’s all about.”

The Next Step

While Rhino Records decides what is next for the Chicago catalogue, Tim is currently working on several film soundtracks, including composing the music score for one of them. He and the band are also discussing the possibility of remixing their classic debut album Chicago Transit Authority; like the Isle Of Wight set, this also resides on a one‑inch eight‑track tape.

Further down the line, Tim is also keen to apply the experience he’s gained on this set to other performances. “Mixing Chicago’s Isle Of Wight performance enabled me to develop some very effective techniques to deal with the issues inherent in all of the Isle Of Wight recordings captured by Pye Studios in 1970. It would be enjoyable to transform the recordings of some of the other artists who performed during this festival, for instance a remix of Emerson, Lake & Palmer, Miles Davis, the Who, the Moody Blues, Jethro Tull, and so many others. There were many iconic performances during this festival that can be elevated into mixes with far greater detail and clarity.”